1. The information below is from a box of typhoid vaccine. VIVOTIF BERNA® Typhoi
ID: 303049 • Letter: 1
Question
1. The information below is from a box of typhoid vaccine.
VIVOTIF BERNA®
Typhoid Vaccine
Oral Ty 21a
Explain how you would know by simply reading this label that this is an attenuated vaccine. (Hint: Vivo means "life" in Latin and the lowercase “a” does stand for attenuated, but these are not the answers I am looking for.)
2. Explain how the bacterium is attenuated in the Vivotif vaccine and why this attenuation prevents the the bacteria in the vaccine from causing typhoid fever. (Note: You will find the answer in the product insert for the drug under “Clinical Pharmacology.” Be specific and thorough in your response.)
3. Typhim Vi® is another typhoid vaccine.
What is the antigen in this vaccine and specifically where does it come from? (Note: Don’t just copy the information from the product insert. Address cell structure and composition of the antigen in your answer.)
4. The Typhim Vi® vaccine is a(n) _____ vaccine.
a. sub-unit
b. inactivated
c. attenuated
5. Explain why re-immunization with the Vivotif® vaccine is recommended every five years, but is recommended every two years for the Typhim Vi® vaccine. (Note: Use your knowledge of immunology to answer this question).
Helpful Links:
Typhoid Vaccine Information
• Immunization Action Coalition Click on “Typhoid.” http://www.immunize.org/fda/
• World Health Organization [WHO] Click on “Typhoid” http://www.who.int/immunization/diseases/en/
Explanation / Answer
2] Vivotif is a live attenuated vaccine for oral administrations only. A complete immunization schedule includes the ingestion of 4 vaccine capsules. Efficacy for this vaccine is found to persist for at least 5 years.
In immunology, attenuated means to weaken or to reduce the virulence of a pathogen.
For preparing attenuated pathogens of typhoid, the pathogens were grown in a new host. A mutation in the bacterium population will help them to infect that host. The mutations will spread and more of mutated pathogens will be produced. This new population of pathogens will not grow well in the original host when it is reintroduced into them. This means they have been attenuated and can be used as vaccines because they will not produce the symptoms of the disease but are potent enough to trigger the immune system to produce antibodies.
3] The antigen is Typhim Vi is the polysaccharide which makes the cell wall of the Salmonella typhi bacteria. It is extracted from the bacterial capsule of the TY2 strain of S. typhi.
4] Option [A] a sub-unit vaccine
This is so because this vaccine does not contain dead or weakened pathogens but presents a typhoid antigen to the immune system. So, the body is not exposed to the pathogen directly.
5] Vivotif vaccine contains attenuated disease-causing pathogens of typhoid. The body is exposed to the pathogens, although weakened and much less virulent than the actual ones. This helps the immune system to respond more strongly to the pathogens and that response lasts for a longer time as compared to Typhim vaccine because Typhim vaccine contains the antigen of typhoid and not the attenuated or dead pathogens. Therefore the immune response is not as strong.
This is why re-immunization with Vivotif is recommended after a longer time gap, i.e. 5 years while for Typhim Vi it is recommended every two years.
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